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Mathematical methods in classical mechanics, classical and quantum field theory, quantum mechanics, statistical mechanics, condensed matter, nuclear and atomic physics.

21 votes
6 answers
3k views

Penrose tilings and noncommutative geometry

Are there "elementary" resources on Penrose Tilings in relation to noncommutative geometry? It's all a big blur to me. There are two transformations S and T that can grow the tilings and every tilin …
john mangual's user avatar
  • 22.8k
17 votes
4 answers
9k views

Noether's theorem in quantum mechanics

In classical mechanics: If a Lagrangian $\mathcal{L}$ is preserved by an infinitesimal change in the state space variables $q_i \to q_i + \varepsilon K_i(q)$, this leads to only second order change in …
john mangual's user avatar
  • 22.8k
16 votes
5 answers
1k views

G-bundles in classical mechanics

The paper Geometry of the Prytz Planimeter described a mechanical instrument whose configuration space is an $S^1$-bundle with an $SU(1,1)$ action. That paper goes on to study the holonomies of variou …
14 votes
1 answer
3k views

Dijkgraaf-Witten TQFT vs. Representation Theory?

From what I had read, group characters can be "glued" together in a topological fashion and there is something to this effect in the paper by Dijkgraaf and Witten. TQFT seems to be a topological gener …
john mangual's user avatar
  • 22.8k
11 votes
2 answers
2k views

the spectrum of the Laplacian and Dirac operator on $S^3$

A paper on supersymmetry in 3-dimensions uses results on the spectra of elliptic operators on $S^3$: The eigenvalues of the vector Laplacian on divergenceless vector fields is $(\ell + 1)^2$ wit …
john mangual's user avatar
  • 22.8k
11 votes
2 answers
1k views

Free Boson Correlator $ \langle X(z)X(w) \rangle =- \ln |z - w| $

In physics papers, the massless free boson has a definition involving an action: $$ S(X) = \frac{1}{8\pi} \int d\sigma^2\, \partial X \overline{\partial X}$$ The random functions $X(z)$ are sample …
john mangual's user avatar
  • 22.8k
9 votes
1 answer
609 views

Matrix-tree theorem via supersymmetry (i.e. Grassman algebras)

The matrix-tree theorem states the number of spanning trees of a graph $G$ is equal to a modified determinant of the adjacency matrix or "graph Laplacian", $\Delta_G$: $$\#\{ \text{spanning trees of } …
john mangual's user avatar
  • 22.8k
8 votes
1 answer
526 views

A q,t-extension of Plancherel Measure thru Yang-Mills Theory ?

Buried in the physics paper by Nekrasov and Okounkov, a strange identity is proven: $$ \prod_{n > 0} (1 - q^n)^{\mu^2-1} = \sum_{\mathbf{k}} q^{|\mathbf{k}|} \prod_{\square \in k} \left( 1 - \frac{\mu …
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7 votes
1 answer
518 views

map from 6-vertex model to domino tiling

I am trying to find a correspondence between 6-vertex model and an Aztec Diamond tiling. Here are the building blocks of the 8-vertex model: There seems to be more than one correspondence. I foun …
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7 votes
0 answers
251 views

Is the Dimer Model a TQFT?

The answer to my question is "yes". Technically, it's a spin-TQFT but now I am trying to make sense of that answer. Dimers on surface graphs and spin structures. I David Cimasoni, Nicolai Resheti …
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7 votes
3 answers
823 views

What is the link between the Domino Tilings and the Ising Model?

Is there a link between the theory of Domino Tilings and the Ising Model? In the global qualitative sense that physicists use, the answer is "yes". The connections could go like this: The dimer m …
john mangual's user avatar
  • 22.8k
6 votes
2 answers
1k views

Categorifications of the Fibonacci Fusion Ring arising from Conformal Field Theory

I was reading about realizations of the "Fibonacci" fusion ring $X \otimes X = X \oplus 1$ in Fusion Categories of Rank 2 by Victor Ostrik. Apparently, there are two of them and they arise in various …
john mangual's user avatar
  • 22.8k
6 votes
0 answers
410 views

Birth-Death Process associated with Orthogonal Polynomials

I have read in various places the following objects are related: orthogonal polynomials birth-death processes Lattice paths continued fractions After a lot of searching online, I found sketches ab …
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  • 22.8k
6 votes
0 answers
397 views

semiclassical proof of Wigner semicircle

In Terence Tao's discussion of the Gaussian Unitary Ensemble, he derives the Dyson and Airy kernels. The GUE is the probability distribution of the eigenvalues of a random Hermitian matrix. \[ \int …
john mangual's user avatar
  • 22.8k
6 votes
1 answer
321 views

Rotations, harmonic oscillators, Gaussians, ladders

I am trying to understand better the quantization of the harmonic oscillator. Here are three ways of thinking about the harmonic oscillator. Eigenfunctions of the differential operator: $H = -\frac{ …
john mangual's user avatar
  • 22.8k

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